Refactor EdgeDetectorCompassProcessor<TPixel>

src/ImageSharp/Processing/Processors/Convolution/EdgeDetectorCompassProcessor{TPixel}.cs

@@ -65,77 +65,112 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
             int minY = Math.Max(0, startY);
             int maxY = Math.Min(source.Height, endY);
 
-            // we need a clean copy for each pass to start from
-            using (ImageFrame<TPixel> cleanCopy = source.Clone())
+            // We need a clean copy for each pass to start from
+            using ImageFrame<TPixel> cleanCopy = source.Clone();
+
+            using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[0], true, this.Source, this.SourceRectangle))
             {
-                using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[0], true, this.Source, this.SourceRectangle))
-                {
-                    processor.Apply(source);
-                }
+                processor.Apply(source);
+            }
 
-                if (kernels.Length == 1)
-                {
-                    return;
-                }
+            if (kernels.Length == 1)
+            {
+                return;
+            }
 
-                int shiftY = startY;
-                int shiftX = startX;
+            int shiftY = startY;
+            int shiftX = startX;
 
-                // Reset offset if necessary.
-                if (minX > 0)
-                {
-                    shiftX = 0;
-                }
+            // Reset offset if necessary
+            if (minX > 0)
+            {
+                shiftX = 0;
+            }
 
-                if (minY > 0)
+            if (minY > 0)
+            {
+                shiftY = 0;
+            }
+
+            // Additional runs
+            for (int i = 1; i < kernels.Length; i++)
+            {
+                using ImageFrame<TPixel> pass = cleanCopy.Clone();
+
+                using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[i], true, this.Source, this.SourceRectangle))
                 {
-                    shiftY = 0;
+                    processor.Apply(pass);
                 }
 
-                var workingRect = Rectangle.FromLTRB(minX, minY, maxX, maxY);
+                ParallelRowIterator.IterateRows(
+                    Rectangle.FromLTRB(minX, minY, maxX, maxY),
+                    this.Configuration,
+                    new RowIntervalAction(source.PixelBuffer, pass.PixelBuffer, minX, maxX, shiftY, shiftX));
+            }
+        }
 
-                // Additional runs.
-                // ReSharper disable once ForCanBeConvertedToForeach
-                for (int i = 1; i < kernels.Length; i++)
+        /// <summary>
+        /// A <see langword="struct"/> implementing the convolution logic for <see cref="EdgeDetectorCompassProcessor{T}"/>.
+        /// </summary>
+        private readonly struct RowIntervalAction : IRowIntervalAction
+        {
+            private readonly Buffer2D<TPixel> targetPixels;
+            private readonly Buffer2D<TPixel> passPixels;
+            private readonly int minX;
+            private readonly int maxX;
+            private readonly int shiftY;
+            private readonly int shiftX;
+
+            /// <summary>
+            /// Initializes a new instance of the <see cref="RowIntervalAction"/> struct.
+            /// </summary>
+            /// <param name="targetPixels">The target pixel buffer to adjust.</param>
+            /// <param name="passPixels">The processed pixels for the current iteration. Cannot be null.</param>
+            /// <param name="minX">The minimum horizontal offset.</param>
+            /// <param name="maxX">The maximum horizontal offset.</param>
+            /// <param name="shiftY">The vertical offset shift.</param>
+            /// <param name="shiftX">The horizontal offset shift.</param>
+            [MethodImpl(InliningOptions.ShortMethod)]
+            public RowIntervalAction(
+                Buffer2D<TPixel> targetPixels,
+                Buffer2D<TPixel> passPixels,
+                int minX,
+                int maxX,
+                int shiftY,
+                int shiftX)
+            {
+                this.targetPixels = targetPixels;
+                this.passPixels = passPixels;
+                this.minX = minX;
+                this.maxX = maxX;
+                this.shiftY = shiftY;
+                this.shiftX = shiftX;
+            }
+
+            /// <inheritdoc/>
+            [MethodImpl(InliningOptions.ShortMethod)]
+            public void Invoke(in RowInterval rows)
+            {
+                for (int y = rows.Min; y < rows.Max; y++)
                 {
-                    using (ImageFrame<TPixel> pass = cleanCopy.Clone())
+                    int offsetY = y - this.shiftY;
+
+                    ref TPixel passPixelsBase = ref MemoryMarshal.GetReference(this.passPixels.GetRowSpan(offsetY));
+                    ref TPixel targetPixelsBase = ref MemoryMarshal.GetReference(this.targetPixels.GetRowSpan(offsetY));
+
+                    for (int x = this.minX; x < this.maxX; x++)
                     {
-                        using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[i], true, this.Source, this.SourceRectangle))
-                        {
-                            processor.Apply(pass);
-                        }
-
-                        Buffer2D<TPixel> passPixels = pass.PixelBuffer;
-                        Buffer2D<TPixel> targetPixels = source.PixelBuffer;
-
-                        ParallelRowIterator.IterateRows(
-                            workingRect,
-                            this.Configuration,
-                            rows =>
-                                {
-                                    for (int y = rows.Min; y < rows.Max; y++)
-                                    {
-                                        int offsetY = y - shiftY;
-
-                                        ref TPixel passPixelsBase = ref MemoryMarshal.GetReference(passPixels.GetRowSpan(offsetY));
-                                        ref TPixel targetPixelsBase = ref MemoryMarshal.GetReference(targetPixels.GetRowSpan(offsetY));
-
-                                        for (int x = minX; x < maxX; x++)
-                                        {
-                                            int offsetX = x - shiftX;
-
-                                            // Grab the max components of the two pixels
-                                            ref TPixel currentPassPixel = ref Unsafe.Add(ref passPixelsBase, offsetX);
-                                            ref TPixel currentTargetPixel = ref Unsafe.Add(ref targetPixelsBase, offsetX);
-
-                                            var pixelValue = Vector4.Max(
-                                                currentPassPixel.ToVector4(),
-                                                currentTargetPixel.ToVector4());
-
-                                            currentTargetPixel.FromVector4(pixelValue);
-                                        }
-                                    }
-                                });
+                        int offsetX = x - this.shiftX;
+
+                        // Grab the max components of the two pixels
+                        ref TPixel currentPassPixel = ref Unsafe.Add(ref passPixelsBase, offsetX);
+                        ref TPixel currentTargetPixel = ref Unsafe.Add(ref targetPixelsBase, offsetX);
+
+                        var pixelValue = Vector4.Max(
+                            currentPassPixel.ToVector4(),
+                            currentTargetPixel.ToVector4());
+
+                        currentTargetPixel.FromVector4(pixelValue);
                     }
                 }
             }